MC68HC08AS32 Datasheet, PDF (136/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

System Integration Module (SIM)
9.6.2 Reset
All reset sources always have higher priority than interrupts and cannot
be arbitrated.
9.6.3 Break Interrupts
The break module can stop normal program flow at a
software-programmable break point by asserting its break interrupt
output. (See Section 11. Break Module (Break).) The SIM puts the
CPU into the break state by forcing it to the SWI vector location. Refer
to the break interrupt subsection of each module to see how the break
state affects each module.
9.6.4 Status Flag Protection in Break Mode
The SIM controls whether status flags contained in other modules can
be cleared during break mode. The user can select to protect flags from
being cleared by properly initializing the break clear flag enable bit
(BCFE) in the SIM break flag control register (SBFCR). (See 9.8.3 SIM
Break Flag Control Register.)
Protecting flags in break mode ensures that set flags will not be cleared
while in break mode. This protection allows registers to be freely read
and written during break mode without losing status flag information.
Setting the BCFE bit enables the clearing mechanisms. Once cleared in
break mode, a flag remains cleared even when break mode is exited.
Status flags with a 2-step clearing mechanism — for example, a read of
one register followed by the read or write of another — are protected,
even when the first step is accomplished prior to entering break mode.
Upon leaving break mode, execution of the second step will clear the
flag as usual.
Advance Information
136
System Integration Module (SIM)
MC68HC08AS32 — Rev. 3.0
MOTOROLA